JP2694415B2 - Conductive rubber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive rubber which has a small variation in electric resistance depending on a measuring position and an applied voltage and has little change with time, and is suitable for manufacturing a transfer roller and a charging roller of a copying machine. It is something.

[0002]

2. Description of the Related Art As a conductive rubber, a rubber containing one kind or two or more kinds of solid conductive agents such as carbon black, graphite or metal powder has been known. Further, for the purpose of making the appearance of the antistatic mat be a color other than black, a phosphoric ester plasticizer and an ionic surfactant are added on the base layer made of the conductive rubber containing the carbon black. It is known to laminate a cover layer made of a conductive rubber containing both (see Japanese Patent Laid-Open No. 61-176098).

[0003]

In a conductive rubber containing a solid conductive agent such as carbon black, the arrangement of the solid conductive agents mixed in the rubber is disturbed as the rubber flows during vulcanization molding. Partly coarse and dense parts occur,
Therefore, there has been a problem that the electrical resistance of the vulcanized molded product is largely different depending on the applied voltage. On the other hand, when not using the solid conductive agent but using both the phosphoric acid ester plasticizer and the ionic surfactant, it is necessary to increase the addition amount in order to obtain the desired resistance value. Had a problem that the rubber surface was sticky.

In order to reduce the variation in electric resistance due to the density of the solid conductive agent, it has been attempted to add the above phosphoric acid ester plasticizer as a liquid conductive agent. In this case, variations in electric resistance due to the density of the solid conductive agent can be reduced, but since the phosphate ester plasticizer has high polarity, the phosphate ester plasticizer can be left unattended for a long time. The agent moves to the rubber surface,
There was a problem that the effect of addition was lost.

According to the present invention, a liquid conductive agent such as a phosphoric acid ester plasticizer and an adsorbent are added to a conductive rubber containing a solid conductive agent to reduce partial variations in electric resistance and variations due to applied voltage. At the same time, the liquid conductive agent is prevented from moving to prevent the electric resistance from changing with time and stabilizes the electric resistance.

[0006]

That is, the present invention provides:
Carbon black, a liquid conductive agent and the liquid conductive agent becomes dispersed an adsorbent property of adsorbing to a rubber containing solid conductive agent such as graphite or metal powder, said liquid
The conductive agent is a phosphate ester plasticizer, and the above-mentioned adsorbent
Is a silicate, and phosphoric acid based on 100 parts by weight of rubber is used.
The content of stealth plasticizer and silicate is 1 to
The conductive rubber is 30 parts by weight and 1 to 60 parts by weight .

The liquid conductive agent used in the present invention is trimethyl phosphate, triethyl phosphate, tributyl phosphate, tree (2 ethylhexyl).
Phosphate, 2-ethylhexyl diphenyl phosphate, tributoxyethyl phosphate, triphenyl phosphate, cresyl diphenyl phosphate, isodecyl diphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, tri (chloroethyl) phosphate, xylenyl diphenyl. phosphate, phosphoric acid ester-based plasticizers such as alkyl allyl phosphates and Tetorakisu (2,4-di-tert-butylphenyl) 4,4'-biphenylene phosphate.

[0008] In addition, Japanese HirakiAkira 59-105037 discloses,
JP-A-60-181142, JP-A-64-925
Japanese Patent Laid-Open No. 8-9, Japanese Patent Laid-Open No. 9358/1988, Japanese Patent Laid-Open No. 2-2
45038 discloses a plasticizer having a known alkylene oxide groups disclosed in JP-A-2-255852 discloses the like may be used together with the phosphoric acid ester plasticizers described above.

In the present invention, an adsorbent capable of adsorbing the above liquid conductive agent is added, and as the adsorbent, the ability to adsorb dioctyl phthalate (DOP) used as a plasticizer for rubber, That is, silicates such as synthetic silicates, anhydrous silicates, and hydrous silicates having a DOP oil absorption of 30 ml / 100 g or more are used .

In the present invention, the solid conductive agent such as carbon black has a volume resistivity of the conductive rubber of 10 ² to.
It is compounded in a range of 10 ¹⁰ Ω · cm so as to have a desired size according to the purpose of use, and the compounding amount of the phosphate ester plasticizer is 1 to 30 parts by weight with respect to 100 parts by weight of rubber. In particular, 3 to 15 parts by weight is preferable, and the amount of the silicate compounded is 1 to 60 parts by weight, particularly 15 to 40 parts by weight, based on 100 parts by weight of rubber.

[0011]

In the conductive rubber of the present invention, the solid conductive agent such as carbon black is mixed with the rubber and the liquid conductive agent is added. Since the electric charge according to the above freely moves through the liquid conductive agent, variations in resistance due to the measurement position and applied voltage are reduced. Furthermore, since the adsorbent of the liquid conductive agent is added, the liquid conductive agent is prevented from moving to the rubber surface, and the change in electric resistance with time is reduced. Moreover ,
Since a phosphoric acid ester plasticizer is used as the liquid conductive agent, the volatility is small and stable, and since a silicate is used as the adsorbent, the adsorption capacity is high and stable.

However, if the compounding amount of the phosphate ester plasticizer is less than 1 part by weight, the desired effect cannot be obtained. On the contrary, if it exceeds 30 parts by weight, it will flow out to the rubber surface and become sticky. Occurs. Further, if the amount of the silicate compounded is less than 1 part by weight, there is no effect. On the contrary, if it exceeds 60 parts by weight, the rubber becomes excessively hard and the workability deteriorates.

[0013]

EXAMPLES Conductive silicone rubber containing carbon black (manufactured by Toshiba Silicone Co., product number "XE23-A49"
03K ") 80 parts by weight, carbon black-free conductive silicone rubber for dilution (manufactured by Toshiba Silicone Co., product number" XE20-A6303 ") 20 parts by weight and a vulcanizing agent (manufactured by Toshiba Silicone, product number" TC-8 "). ) 1.5 parts by weight of conductive rubber is added to which tributyl phosphate as a liquid conductive agent and silicate (KOFRAN CHEMICAL, trade name "Tixorex 15") as an adsorbent are added. By mixing, various conductive rubbers having different compositions were prepared.

A charging roller for a copying machine (roller diameter: 14 mm, roller width: 222 mm, using the above-mentioned various conductive rubbers)
A core metal diameter: 8 mm) was molded by using an injection mold. Vulcanization was performed at 164 ° C. for 30 minutes. The obtained charging roller is placed on a flat copper plate, and a load of 250 g is applied to each cored bar protruding from both ends to bring the rubber layer surface of the charging roller into close contact with the copper plate. While applying a DC voltage and rolling the charging roller, the current flowing between the cored bar and the copper plate was measured to calculate the resistance of the rubber layer. The results are shown in Table 1 below.

Table 1 Adsorbent Liquid conductive agent Resistance value variation (parts by weight) (parts by weight) (1 × 10 ⁶ Ω) (maximum / minimum) Comparative example 1 20.0 − 4000 to infinity Infinite comparison 2 to 2.4 14 ~ 4000 285 Example 1 2.0 2.4 13 ~ 300 23 Example 2 20.0 2.4 15 ~ 100 6.6 Example 3 25.0 2.4 100 ~ 200 2.0 Example 4 30.0 2.4 200 ~ 400 2.0 Example 5 25.0 3.0 80 ~ 160 2.0 Example 6 25.0 3.2 70 to 150 2.1 Example 7 25.0 4.0 50 to 100 2.0 Example 8 25.0 10.0 20 to 80 4.0 Example 9 58.0 15.0 15 to 150 10.0 Example 10 25.0 28.0 10 to 120 12.0

As can be seen from Table 1 above, Examples 1 to 1 containing tributyl phosphate as the liquid conductive agent and silicate as the adsorbent (trade name "Tixorex 15" manufactured by KOFRAN CHEMICAL).
When 0, the variation in the resistance value (the ratio of the maximum resistance value to the minimum resistance value) becomes small. On the other hand, Comparative Example 1 containing no liquid conductive agent had a large variation in resistance value, and Comparative Example 2 containing no adsorbent had stickiness on the surface.

The admixture amount in Example 7 was set to 5
Comparative Example 3 by reducing the amount to parts by weight and omitting the addition of the liquid conductive agent.
The charging roller of was prepared. The charging rollers of Example 7 and Comparative Example 3 described above were fixed, and the resistance when the applied voltage was changed was compared. The result is shown in FIG. As shown in FIG. 1, in Example 7, even when the voltage was gradually increased from 0 volt, the resistance value hardly changed up to 1500 volt. However, in Comparative Example 3, the resistance value drastically decreased as the applied voltage increased, and in Comparative Example 3, when the voltage exceeded 900 V, a current exceeding the allowable limit flowed and measurement became impossible. In Comparative Example 3, there was a large partial variation in the resistance value, and there was a portion where almost no current flowed.
It was measured in a relatively flowing part.

Further, the charging rollers of Example 7 and Comparative Example 3 described above were fixed, and changes in resistance value with application time were compared. The result is shown in FIG. Example 7 is applied voltage 2
It showed an almost constant resistance value at 000 volts for 30 minutes. On the other hand, Comparative Example 3 showed a substantially constant resistance value at an applied voltage of 900 volts.

Further, the charging rollers of Example 7 and Comparative Example 3 were rotated and the variations in resistance (maximum / minimum) were compared. The results are shown in Table 2 below. Table 2 Applied voltage (V) Resistance (1 × 10 ⁶ Ω) Maximum / Minimum Example 7 2000 50.0 to 100 2 Comparative Example 3 900 3.3 to 1300 394

In Example 2 of Table 1, the liquid conductive agent
The door Ribuchiru phosphate (Daihachi Chemical Co., Ltd., trade name "TBP") and tricresyl phosphate was changed to (Daihachi Chemical Co., Ltd., trade name "TCP"), except that the the addition of 3 parts by weight example 11 in the same manner, 1
The conductive rubber of No. 2 was manufactured, a charging roller was manufactured in the same manner using this conductive rubber, and the resistance of the rubber layer was measured. Immediately after the above charging roller was immersed in water for 1 day and taken out, and after being taken out of water and dried for 3 days, the resistance was determined in the same manner as above. Table 3 shows the types of the liquid conductive agent, and Table 4 shows the resistance values obtained by the measurement and the ratios of the maximum resistance value to the minimum resistance value before the immersion, immediately after the immersion and 3 days after the immersion. It should be noted that Comparative Example 4 was one containing neither a liquid conductive agent nor an adsorbent.

[0021] Example 12 Tricresyl phosphate

[0022]

As is clear from Tables 3 and 4, Examples 11 and 12 are affected by water due to the water absorption of the liquid conductive agent, and the resistance value changes before and after immersion. the degree of change or significantly small in comparison with Comparative example 4
Was .

[0024]

As described above, the conductive rubber of the present invention is obtained by dispersing a liquid conductive agent and an adsorbent that adsorbs the liquid conductive agent in a rubber containing a solid conductive agent such as carbon black. Therefore, variations in resistance due to position and voltage are reduced, and electric resistance does not change with time. Moreover, since the phosphoric acid ester-based plasticizer is used as the liquid conductive agent and the silicate is used as the adsorbent, the above variations and the change with time become small, and the performance as the conductive rubber is more stable. To do. Furthermore, since the contents of the phosphoric acid ester-based plasticizer and the silicate are limited to 1 to 30 parts by weight and 1 to 60 parts by weight, respectively, stability of the above performance and elasticity as a rubber are not lost, Moreover, the surface is not sticky.

[Brief description of the drawings]

FIG. 1 is a graph showing changes in resistance according to voltage in Examples and Comparative Examples.

FIG. 2 is a graph showing changes in resistance over time of Examples and Comparative Examples.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location // G03G 15/02 101 G03G 15/02 101 15/16 103 15/16 103

Claims (1)

(57) [Claims] 1. A carbon black, it was dispersed adsorbent property of adsorbing a liquid conductive agent and said liquid conductive material in a rubber containing solid conductive agent such as graphite or metal powder
The above liquid conductive agent is a phosphate ester plasticizer.
The above adsorbent is silicate, and 100 parts by weight of rubber is used.
Of Phosphate Plasticizers and Silicates
1 to 30 parts by weight and 1 to 60 parts by weight, respectively.
Conductive rubber, characterized in that that.